exhaustivity support for enums

9 files changed, 86 insertions, 56 deletions

diff --git a/compiler/src/dotty/tools/dotc/config/Printers.scala b/compiler/src/dotty/tools/dotc/config/Printers.scala
index 002d0f933..a77607d18 100644
--- a/compiler/src/dotty/tools/dotc/config/Printers.scala
+++ b/compiler/src/dotty/tools/dotc/config/Printers.scala
@@ -31,4 +31,5 @@ object Printers {
   val cyclicErrors: Printer = noPrinter
   val pickling: Printer = noPrinter
   val inlining: Printer = noPrinter
+  val exhaustivity: Printer = noPrinter
 }
diff --git a/compiler/src/dotty/tools/dotc/transform/PostTyper.scala b/compiler/src/dotty/tools/dotc/transform/PostTyper.scala
index a0fe55a5b..bacb88091 100644
--- a/compiler/src/dotty/tools/dotc/transform/PostTyper.scala
+++ b/compiler/src/dotty/tools/dotc/transform/PostTyper.scala
@@ -111,7 +111,7 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer  { thisTran
 
     private def transformMemberDef(tree: MemberDef)(implicit ctx: Context): Unit = {
       val sym = tree.symbol
-      if (sym.is(CaseVal, butNot = Module | Method)) registerChild(sym, sym.info)
+      if (sym.is(CaseVal, butNot = Method | Module)) registerChild(sym, sym.info)
       sym.transformAnnotations(transformAnnot)
     }
 
@@ -233,7 +233,10 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer  { thisTran
 
             // Add Child annotation to sealed parents unless current class is anonymous
             if (!sym.isAnonymousClass) // ignore anonymous class
-              sym.asClass.classInfo.classParents.foreach(registerChild(sym, _))
+              sym.asClass.classInfo.classParents.foreach { parent =>
+                val sym2 = if (sym.is(Module)) sym.sourceModule else sym
+                registerChild(sym2, parent)
+              }
 
             tree
           }
diff --git a/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala b/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
index 8d926fcf0..41196014e 100644
--- a/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
+++ b/compiler/src/dotty/tools/dotc/transform/patmat/Space.scala
@@ -13,6 +13,7 @@ import core.StdNames._
 import core.NameOps._
 import core.Constants._
 import reporting.diagnostic.messages._
+import config.Printers.{ exhaustivity => debug }
 
 /** Space logic for checking exhaustivity and unreachability of pattern matching
  *
@@ -29,7 +30,6 @@ import reporting.diagnostic.messages._
  *      4. For a case class Kon(x1: T1, x2: T2, .., xn: Tn), if S1, S2, ..., Sn
  *          are spaces, then `Kon(S1, S2, ..., Sn)` is a space.
  *      5. A constant `Const(value, T)` is a point in space
- *      6. A stable identifier `Var(sym, T)` is a space
  *
  *  For the problem of exhaustivity check, its formulation in terms of space is as follows:
  *
@@ -70,9 +70,6 @@ case class Or(spaces: List[Space]) extends Space
 /** Point in space */
 sealed trait Point extends Space
 
-/** Point representing variables(stable identifier) in patterns */
-case class Var(sym: Symbol, tp: Type) extends Point
-
 /** Point representing literal constants in patterns */
 case class Const(value: Constant, tp: Type) extends Point
 
@@ -97,6 +94,9 @@ trait SpaceLogic {
   /** Get components of decomposable types */
   def decompose(tp: Type): List[Space]
 
+  /** Display space in string format */
+  def show(sp: Space): String
+
   /** Simplify space using the laws, there's no nested union after simplify */
   def simplify(space: Space): Space = space match {
     case Kon(tp, spaces) =>
@@ -137,7 +137,7 @@ trait SpaceLogic {
     def tryDecompose1(tp: Type) = canDecompose(tp) && isSubspace(Or(decompose(tp)), b)
     def tryDecompose2(tp: Type) = canDecompose(tp) && isSubspace(a, Or(decompose(tp)))
 
-    (a, b) match {
+    val res = (a, b) match {
       case (Empty, _) => true
       case (_, Empty) => false
       case (Or(ss), _) => ss.forall(isSubspace(_, b))
@@ -162,12 +162,11 @@ trait SpaceLogic {
       case (Const(_, _), Or(ss)) => ss.exists(isSubspace(a, _))
       case (Const(_, _), _) => false
       case (_, Const(_, _)) => false
-      case (Var(x, _), Var(y, _)) => x == y
-      case (Var(_, tp1), Typ(tp2, _)) => isSubType(tp1, tp2) || tryDecompose2(tp2)
-      case (Var(_, _), Or(ss)) => ss.exists(isSubspace(a, _))
-      case (Var(_, _), _) => false
-      case (_, Var(_, _)) => false
     }
+
+    debug.println(s"${show(a)} < ${show(b)} = $res")
+
+    res
   }
 
   /** Intersection of two spaces  */
@@ -175,7 +174,7 @@ trait SpaceLogic {
     def tryDecompose1(tp: Type) = intersect(Or(decompose(tp)), b)
     def tryDecompose2(tp: Type) = intersect(a, Or(decompose(tp)))
 
-    (a, b) match {
+    val res = (a, b) match {
       case (Empty, _) | (_, Empty) => Empty
       case (_, Or(ss)) => Or(ss.map(intersect(a, _)).filterConserve(_ ne Empty))
       case (Or(ss), _) => Or(ss.map(intersect(_, b)).filterConserve(_ ne Empty))
@@ -211,19 +210,11 @@ trait SpaceLogic {
         else if (canDecompose(tp1)) tryDecompose1(tp1)
         else Empty
       case (_, Const(_, _)) => Empty
-      case (Var(x, _), Var(y, _)) =>
-        if (x == y) a else Empty
-      case (Var(_, tp1), Typ(tp2, _)) =>
-        if (isSubType(tp1, tp2)) a
-        else if (canDecompose(tp2)) tryDecompose2(tp2)
-        else Empty
-      case (Var(_, _), _) => Empty
-      case (Typ(tp1, _), Var(_, tp2)) =>
-        if (isSubType(tp2, tp1)) b
-        else if (canDecompose(tp1)) tryDecompose1(tp1)
-        else Empty
-      case (_, Var(_, _)) => Empty
     }
+
+    debug.println(s"${show(a)} & ${show(b)} = ${show(res)}")
+
+    res
   }
 
   /** The space of a not covered by b */
@@ -231,7 +222,7 @@ trait SpaceLogic {
     def tryDecompose1(tp: Type) = minus(Or(decompose(tp)), b)
     def tryDecompose2(tp: Type) = minus(a, Or(decompose(tp)))
 
-    (a, b) match {
+    val res = (a, b) match {
       case (Empty, _) => Empty
       case (_, Empty) => a
       case (Typ(tp1, _), Typ(tp2, _)) =>
@@ -275,15 +266,11 @@ trait SpaceLogic {
         if (canDecompose(tp1)) tryDecompose1(tp1)
         else a
       case (_, Const(_, _)) => a
-      case (Var(x, _), Var(y, _)) =>
-        if (x == y) Empty else a
-      case (Var(_, tp1), Typ(tp2, _)) =>
-        if (isSubType(tp1, tp2)) Empty
-        else if (canDecompose(tp2)) tryDecompose2(tp2)
-        else a
-      case (Var(_, _), _) => a
-      case (_, Var(_, _)) => a
     }
+
+    debug.println(s"${show(a)} - ${show(b)} = ${show(res)}")
+
+    res
   }
 }
 
@@ -298,16 +285,14 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
    */
   def project(pat: Tree, roundUp: Boolean = true)(implicit ctx: Context): Space = pat match {
     case Literal(c) => Const(c, c.tpe)
-    case _: BackquotedIdent => Var(pat.symbol, pat.tpe)
+    case _: BackquotedIdent => Typ(pat.tpe, false)
     case Ident(_) | Select(_, _) =>
       pat.tpe.stripAnnots match {
         case tp: TermRef =>
           if (pat.symbol.is(Enum))
             Const(Constant(pat.symbol), tp)
-          else if (tp.underlyingIterator.exists(_.classSymbol.is(Module)))
-            Typ(tp.widenTermRefExpr.stripAnnots, false)
           else
-            Var(pat.symbol, tp)
+            Typ(tp, false)
         case tp => Typ(tp, false)
       }
     case Alternative(trees) => Or(trees.map(project(_, roundUp)))
@@ -345,7 +330,9 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
   /** Is `tp1` a subtype of `tp2`?  */
   def isSubType(tp1: Type, tp2: Type): Boolean = {
     // check SI-9657 and tests/patmat/gadt.scala
-    erase(tp1) <:< erase(tp2)
+    val res = erase(tp1) <:< erase(tp2)
+    debug.println(s"${tp1.show} <:< ${tp2.show} = $res")
+    res
   }
 
   def isEqualType(tp1: Type, tp2: Type): Boolean = tp1 =:= tp2
@@ -373,6 +360,8 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       }
     }
 
+    debug.println(s"candidates for ${tp.show} : [${children.map(_.show).mkString(", ")}]")
+
     tp match {
       case OrType(tp1, tp2) => List(Typ(tp1, true), Typ(tp2, true))
       case _ if tp =:= ctx.definitions.BooleanType =>
@@ -385,7 +374,9 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
       case _ =>
         val parts = children.map { sym =>
           if (sym.is(ModuleClass))
-            sym.asClass.classInfo.selfType
+            refine(tp, sym.sourceModule.termRef)
+          else if (sym.isTerm)
+            refine(tp, sym.termRef)
           else if (sym.info.typeParams.length > 0 || tp.isInstanceOf[TypeRef])
             refine(tp, sym.typeRef)
           else
@@ -393,13 +384,26 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
         } filter { tpe =>
           // Child class may not always be subtype of parent:
           // GADT & path-dependent types
-          tpe <:< expose(tp)
+          val res = tpe <:< expose(tp)
+          if (!res) debug.println(s"unqualified child ousted: ${tpe.show} !< ${tp.show}")
+          res
         }
 
+        debug.println(s"${tp.show} decomposes to [${parts.map(_.show).mkString(", ")}]")
+
         parts.map(Typ(_, true))
     }
   }
 
+  // simplify p.Case$.This.m => p.Case.m
+  def simplifyPrefix(tp: Type): Type = tp match {
+    case tp @ ThisType(mcls: TypeRef) if mcls.symbol.sourceModule.exists  =>
+      TermRef(simplifyPrefix(mcls.prefix), mcls.symbol.sourceModule.asTerm)
+    case tp @ TypeRef(prefix, _) => tp.derivedSelect(simplifyPrefix(prefix))
+    case tp @ TermRef(prefix, _) => tp.derivedSelect(simplifyPrefix(prefix))
+    case _ => tp
+  }
+
   /** Refine tp2 based on tp1
    *
    *  E.g. if `tp1` is `Option[Int]`, `tp2` is `Some`, then return
@@ -409,20 +413,26 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
    *  `path2`, then return `path1.B`.
    */
   def refine(tp1: Type, tp2: Type): Type = (tp1, tp2) match {
-    case (tp1: RefinedType, _) => tp1.wrapIfMember(refine(tp1.parent, tp2))
+    case (tp1: RefinedType, _: TypeRef) => tp1.wrapIfMember(refine(tp1.parent, tp2))
     case (tp1: HKApply, _) => refine(tp1.superType, tp2)
-    case (TypeRef(ref1: TypeProxy, _), tp2 @ TypeRef(ref2: TypeProxy, name)) =>
-      if (ref1.underlying <:< ref2.underlying) TypeRef(ref1, name) else tp2
+    case (TypeRef(ref1: TypeProxy, _), tp2 @ TypeRef(ref2: TypeProxy, _)) =>
+      if (ref1.underlying <:< ref2.underlying) tp2.derivedSelect(ref1) else tp2
+    case (TypeRef(ref1: TypeProxy, _), tp2 @ TermRef(ref2: TypeProxy, _)) =>
+      if (ref1.underlying <:< ref2.underlying) tp2.derivedSelect(ref1) else tp2
     case _ => tp2
   }
 
   /** Abstract sealed types, or-types, Boolean and Java enums can be decomposed */
   def canDecompose(tp: Type): Boolean = {
-    tp.classSymbol.is(allOf(Abstract, Sealed)) ||
+    val res = tp.classSymbol.is(allOf(Abstract, Sealed)) ||
       tp.classSymbol.is(allOf(Trait, Sealed)) ||
       tp.isInstanceOf[OrType] ||
       tp =:= ctx.definitions.BooleanType ||
       tp.classSymbol.is(Enum)
+
+    debug.println(s"decomposable: ${tp.show} = $res")
+
+    res
   }
 
   /** Show friendly type name with current scope in mind
@@ -475,13 +485,11 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     def doShow(s: Space, mergeList: Boolean = false): String = s match {
       case Empty => ""
       case Const(v, _) => v.show
-      case Var(x, _) => x.show
+      case Typ(tp: TermRef, _) => tp.symbol.showName
       case Typ(tp, decomposed) =>
         val sym = tp.widen.classSymbol
 
-        if (sym.is(ModuleClass))
-          showType(tp)
-        else if (ctx.definitions.isTupleType(tp))
+        if (ctx.definitions.isTupleType(tp))
           signature(tp).map(_ => "_").mkString("(", ", ", ")")
         else if (sym.showFullName == "scala.collection.immutable.::")
           if (mergeList) "_" else "List(_)"
@@ -523,7 +531,9 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     }
 
     val Match(sel, cases) = tree
-    isCheckable(sel.tpe.widen.deAnonymize.dealiasKeepAnnots)
+    val res = isCheckable(sel.tpe.widen.deAnonymize.dealiasKeepAnnots)
+    debug.println(s"checkable: ${sel.show} = $res")
+    res
   }
 
 
@@ -584,7 +594,11 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
     val selTyp = sel.tpe.widen.deAnonymize.dealias
 
 
-    val patternSpace = cases.map(x => project(x.pat)).reduce((a, b) => Or(List(a, b)))
+    val patternSpace = cases.map({ x =>
+      val space = project(x.pat)
+      debug.println(s"${x.pat.show} projects to ${show(space)}")
+      space
+    }).reduce((a, b) => Or(List(a, b)))
     val uncovered = simplify(minus(Typ(selTyp, true), patternSpace))
 
     if (uncovered != Empty)
diff --git a/tests/patmat/enumColor.scala b/tests/patmat/enumColor.scala
new file mode 100644
index 000000000..60d610d0d
--- /dev/null
+++ b/tests/patmat/enumColor.scala
@@ -0,0 +1,12 @@
+ enum Color {
+   case Red, Green, Blue
+ }
+
+ object Test {
+   def f(color: Color) = {
+     import Color._
+     color match {
+       case Red | Green | Blue =>
+     }
+  }
+}
diff --git a/tests/patmat/patmat-indent.check b/tests/patmat/patmat-indent.check
index 79845ebcf..4f0ec4dd9 100644
--- a/tests/patmat/patmat-indent.check
+++ b/tests/patmat/patmat-indent.check
@@ -1,3 +1,3 @@
 9: Pattern Match Exhaustivity: Nil
-23: Pattern Match Exhaustivity: _: Boolean
+23: Pattern Match Exhaustivity: true, false
 27: Pattern Match Exhaustivity: _: Int
diff --git a/tests/patmat/patmat-indent.scala b/tests/patmat/patmat-indent.scala
index ef25bb2c7..a2b18e7fb 100644
--- a/tests/patmat/patmat-indent.scala
+++ b/tests/patmat/patmat-indent.scala
@@ -1,5 +1,5 @@
 object Test {
-  val Nil = scala.Nil
+  val Nil: scala.collection.immutable.Nil.type = scala.collection.immutable.Nil
   val X = 5
 
   object Inner {
diff --git a/tests/patmat/t6420.check b/tests/patmat/t6420.check
index 73acf1454..c15701594 100644
--- a/tests/patmat/t6420.check
+++ b/tests/patmat/t6420.check
@@ -1 +1 @@
-5: Pattern Match Exhaustivity: (Nil, _), (List(_, _), _), (Nil, Nil), (Nil, List(_, _)), (List(_, _), Nil), (List(_, _), List(_, _)), (_, Nil), (_, List(_, _))
+5: Pattern Match Exhaustivity: (Nil, _), (List(true, _), _), (List(false, _), _), (_, Nil), (_, List(true, _)), (_, List(false, _))
diff --git a/tests/patmat/t7285.check b/tests/patmat/t7285.check
index 1c2841920..d40b77e4b 100644
--- a/tests/patmat/t7285.check
+++ b/tests/patmat/t7285.check
@@ -1,3 +1,3 @@
 15: Pattern Match Exhaustivity: (Up, Down)
 33: Pattern Match Exhaustivity: Down
-51: Pattern Match Exhaustivity: (Base.Up, Base.Down)
+51: Pattern Match Exhaustivity: (Up, Down)
diff --git a/tests/patmat/t7466.check b/tests/patmat/t7466.check
index 35227484e..af596399b 100644
--- a/tests/patmat/t7466.check
+++ b/tests/patmat/t7466.check
@@ -1 +1 @@
-8: Pattern Match Exhaustivity: (_, _)
+8: Pattern Match Exhaustivity: (true, _), (false, _), (_, true), (_, false)